Among the following, the correct example of a free-radical substitution reaction is:

1.
2.
3.
4.

Which of the following reactions, in the presence of anhydrous AlCl₃, leads to the formation of ethylbenzene (Ph–Et)?

1. ${\mathrm{CH}}_3-\mathrm{CH}={\mathrm{CH}}_2+{\mathrm{C}}_6{\mathrm{H}}_6$

2. ${\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2+{\mathrm{C}}_6{\mathrm{H}}_6$

3. ${\mathrm{H}}_3\mathrm{C}-{\mathrm{CH}}_3+{\mathrm{C}}_6{\mathrm{H}}_6$

4. ${\mathrm{H}}_3\mathrm{C}-{\mathrm{CH}}_2\mathrm{OH}+{\mathrm{C}}_6{\mathrm{H}}_6$